As is known, a spectrometer enables measuring light in a certain spectral range depending on wavelengths. The core pieces of each spectrometer are a dispersive element such as a grating or a prism the light, the spectral distribution of which is to be determined, is incident to and which disperses the incident light into its spectral constituents, and a respective detector for acquiring one or several of the spectral constituents. FIG. 6 shows a classical arrangement of a grating spectrometer. A moveable grating 900 is illuminated through an entrance slot and a bundling element (not shown) by a beam of light 902, the spectral distribution of which is to be determined. The movable grating 900 is hinged to an axis that runs in parallel to the grating lines. Grating 900 is adjusted quasi-statistically, typically via a stepper motor. The light 906 split according to wavelengths—more precisely a spectral constituent thereof—is detected by means of a detector element 908, while the grating 900 is moved into different positions. This way, the light 906, which is split according to wavelengths in a plane perpendicular to the axis of rotation, is sampled by means of detector 908, while the measurement signals thereof are recorded correspondingly in order to determine the spectral distribution of the beam of light 902.
Spectrometers are used, among others, in so-called spectral imaging systems. A spectral imaging system is a sensor system that simultaneously acquires spectral and spatial information, which provides the entire mechanical, electronical and optical periphery, which analyses combination data and forwards the analytical values. In the visible spectral range (380-780 nm wavelength), the demands made on spectral imaging systems may be sufficiently well met by systems with two-dimensional detector arrangements (CCD image sensors and/or so-called 2D array detectors). Here, the geometrical line to be evaluated is imaged via a fixedly mounted diffraction grating onto the detector surface. A representation is then obtained on the two-dimensional detector, wherein one direction corresponds to the geometrical component and the other to the wavelength. Thus, a spectral intensity distribution may be determined for each geometrical location of the line. Suitable detectors are available with a very large number of detector elements, presently up to the double-digit million area, for example as a chip with 3,000×5,000 elements and more.
Due to natural and technical constraints, measurements specifically in the infrared spectral range are often necessary. This is, almost without exception, indispensable especially for applications that demand measurements during the night without direct illumination by the sun or additional artificial light sources. The infrared spectral range lies above the sensitivity limit of silicon detectors (1,300 nm wavelength). In this range, the availability of suitable detectors, particularly of two-dimensional arrangements, are very limited. Monolithically integrated devices are presently very expensive. The number of detector elements is comparably low already in the case of line arrangements. Presently, lines with 256-512 elements are commercially available. Under the use of infrared spectrometers, which, as a rule, comprise InGaAs (Indium-Gallium-Arsenide) line detectors and fixedly mounted gratings, such systems may be realized by combination with a so-called sample unit for beam control. The system expenditure, however, is very high and the systems operate conditionally low with simultaneously limited picture-dot resolution. The complex technology is sensitive with regard to the adjustment of the assemblies to one another and with regard to interferences from the environment.
One conceivable realization alternative for the solution of the problem comprising an oscillating grating chip, as described in publication document WO 03069290 A1, has the disadvantage that the spectral resolution through the movement area takes place with a very fine resolution, which is, however, not advantageous due to the optical constraints, which, however, provides for the geometrical resolution by the relatively small number of detector elements. A geometrical resolution of only 256-512 dots is for a number of applications not sufficient.